The invention relates to a rotary regenerative heat-exchanger, provided with a rotor which is accommodated in a stationary rotor housing and which contains a regenerative filling mass. Through the rotor a cold gas flow and a hot gas flow, admitted on both sides of the rotor via a first and a second inlet of the housing, respectively, and having a mutually different variable pressure and velocity, can flow in the axial direction in couterflow, the variable gas flows exerting mutually opposed variable forces on the rotor due to the flow resistance of the filling mass. Sealing members are provided between the rotor end faces and the housing in order to separate the two gas flows.
Rotary heat-exchangers of the kind set forth are known, for example, from German Patent Specification No. 954,061. They are used particularly in power sources such as gas turbines and hot-gas reciprocating engines in order to preheat the cold and compressed combustion air supplied to these power sources by means of the hot flue gases discharged from the said power sources.
Because of the higher viscosity and the higher velocity inherent of the larger volume flow of the hot flue gas of lower pressure with respect to the cold combustion air of higher pressure, the flue gas in the heat exchanger known from said German Patent Specification No. 954,061, exerts a force on the rotor in the axial direction which exceeds the force exerted thereon in the opposite direction by the combustion air. In the case of variations of the load of the power source, the combustion air flow and the flue gas flow also vary, and hence the forces exerted on the rotor by these flows also vary.
On the lower-temperature side of the rotor of this known rotary heat-exchanger, where the inlet for cold air and the outlet for cooled flue gas are situated, there are provided stationary springs which keep the sealing members, constructed as plates, pressed against sealing faces on the relevant end face of the rotor. These springs are pre-tensioned such that in all operating conditions they also keep the sealing faces on the other rotor end face pressed against cooperating, stationary sealing members on the neighbouring opposite rotor housing portion. This means that the sum of the forces exerted by the springs on the rotor should be larger than the maximum resultant force exerted on the springs by the rotor due to the opposed gas flows through the filling mass. The maximum resultant force due to the gas flows occurs at the highest load of the heat-exchanger, which is to say at the largest gas flows, which corresponds to the maximum loading of the power source.
It is a drawback of this known construction that in every operating condition, so also and notably at small gas flows, the rotor is subject to the maximum spring load. This implies that the rotor must always be driven at a torque which is at least equal to the maximum friction torque between rotor and sealing members which is mainly determined by the spring force and the friction coefficient between the sealing members and the rotor sealing faces.
Because of the high spring force required, little freedom exists as regards the choice of the springs, and springs having a high rigidity must be used. The high spring force leads to quick wear of the sealing members and rotor sealing faces.